Actually the "Forward Unto Dawn" web series directors cut with an additional 15 minutes will be a high definition download with the purchase of the Limited Edition, not on a disk. What I have read is that it will only be available on Halo Waypoint on the 360 dashboard, just like the "Making of Halo: Reach" when you bought the limited edition for it.

I'm happy that it's up to a 1080p download, but I would like to be able to store it on my CPU.

This advertisement is actually just a stand alone story arc. The actual movie will have mostly physical sets instead of green screens.